Heat oil in a large pan over medium-high heat. Splutter mustard seeds. Add ginger and garlic. Saute, stirring occasionally, until lightly browned. Add curry leaves.

Reduce the heat to low. Stir in ground turmeric, ground fenugreek, red chili powder and asafoetida. Saute for a minute. Add white vinegar, enough salt and water (I added around ½ cup water) to make the sauce.

Increase the heat to medium-high. Bring to the boil. Reduce heat, and simmer for 2 minutes. Stir in celery. Cook, covered, for 2-3 minutes or until celery turns soft and tender. Remove from heat.

Once cooled, transfer the pickle to a sterilized jar. This pickle is best eaten after 2-3 days. Once opened, make sure you store it in the refrigerator.